[TenTec] continuing: Omni 6+ no receive and very low power on 12/15 m

Bob McGraw K4TAX rmcgraw at blomand.net
Sun Apr 29 23:12:54 EDT 2018


The best thing is to pull the Low Pass Filter board and check all of the 
relays.  This can be done with the relays on the board. The coils are 
wired parallel.  Typical resistance for the pair of good relay coils as 
I recall will be about 450 ohms, if a relay coil is open then you'll see 
about 900 ohms.    The relay pairs for the 10/12M band and the 17/15M 
band will measure a bit higher as there are inductors in series with the 
coils.

The 10M and 12M bands are handled by K2 and K3 where as the 15M and 17M 
band is handled by K4 and K5.   Also check the inductors which are in 
series with the relay coils.   Those are L12, L13, L14 & L15   I have 
found instances where one or more may open.

Your description of no output on 12M controlled by K2 & k3 and 15M 
controlled by K4 & k5 indicates both filters sections are not switching 
correctly.    I doubt than any of the specific filter inductors or 
capacitors have failed.     Relays are prone to have open coils.

As to no receive, this is more likely on the Front End Band Pass Filter 
board.  There are 2 diodes per filter sections.  You can check them on 
the board with a normal diode test using an ohm meter.   Replace any 
which are suspect.

73
Bob, K4TAX


On 4/29/2018 8:40 PM, Steve Bookout wrote:
> Hello all,
>
> Several days ago, I reported my Omni 6+ had no power or receive on 12 
> meters and 15 meters.  From what I remembered and what I saw here, I 
> thought it would be in the output filters.  I bought and received some 
> replacement relays and installed them.  When I checked the ones I 
> removed, they were fine.  Put it back together and fired it up, with 
> the same results.
>
> Tore into it again.  Made sure I had 12 volts on the connector 
> terminal when the switch was on 15 meters.   I applied my external 12 
> volts to the dc input connector (#14?) and relays would click just 
> fine.   Inspected the 15 meter trace under a magnifier and checked the 
> 100 ohm R's on one end of the 12 volt buss and the inductors on the 
> other end.  In the selected filter, all L and C components looked to 
> have nice shiny and clean solder joints.    I removed all caps 
> specific to the 15 meter filter and checked them.  I removed 
> everything but the inductors specific to 15 meters
>
> My actual power is about 1 watt out, not totally zero.
>
> What else might cause this issue?  I'm confident I've done all I can 
> on the LP filter board.  Or, does someone have a suggestion?
>
> 73 de Steve, NR4M
>
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